I've progressed to the point on my Leopard 2 that it's time to paint. Obviously I'll do the normal camo first, but then I need to dirty it up big time, as Canadian Leopards in Afghanistan are extremely dirty. I'll link some photos, as they are extremely large and I don't want to stretch the screens of everyone. Any idea how I'd do this?

There's a number of ways Cory. You could use some of the MIG mud/dust products, but that's relatively expensive, or use the same stuff made yourself. Basically, a mixture of dry pastel dust, and a slurry mixed with the dust and Future, or even water.
The bottom section of the vehicle and around the road wheels and tracks can be done by building-up progressive layers of dry-brushed colours, and the dust etc on the horizontal surfaces could be done with pastels.
You could even mix real earth dust with water, and brush this on, for heavier 'dirt' areas; once dry, it will look like what it actually is - dried mud or heavy dust, depending on the application. The possible disadvantage of this method is that the finish can be disturbed and/or cracked with progressive handling, as it's not really possible to seal this without altering the texture and colour.

this is pretty good colour as a starter and can be dry brushed over later to lighten the colour and add eye shadow to it if you think its necessary. I have included a few pics of a Marder 1 A5 im currently working on using these techniques and paint ranges. hope this is helpful!

The wheels were dry brushed first, then had "armageddon dust" applied, these will be lightened later and dusted later.

"armageddon dust" applied to the treads, then gone over with black and a dry brush of silver before finally applying a black wash to achieved the worn metal look where the tread makes contact

"armageddon dust" aaplied to the skirts of the Marder, which will be lightened using drybrushing, and then dusted with a sand coloured eye shadow

Polyfilla (or whatever your local equivalent is called) makes good dust. It's the stuff you mix with water for repairing plaster. For a darker dust I use a similar powder which is a greyish tile grout.

The tile grout,properly mixed with water,scimmed on a base and allowed to set makes excellent concrete too.